• 청정기술
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• 제27권2호
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• pp.115-123
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• 2021

본 연구는 무기 실리카 껍질(shell)과 유기 고분자 코어(core)로 구성된 매우 균일한 유-무기 복합체 입자 제조의 방법에 관한 것이다. 먼저, 미세유체 기술을 이용하여 균일한 크기를 지니는 유기 고분자 코어 입자를 제조하였다. 코어 입자의 제조 과정에서 코어 입자의 제조 과정에서 광 경화성 유기 물질이 포함된 분산상과 연속상의 유속을 독립적으로 제어함으로써 균일한 액적을 형성하였다. 액적이 형성됨과 동시에, 미세유체 채널의 말단에서 자외선 조사에 의해 액적이 광중합 되어 코어 입자로 형성된다. 더불어, 폴리알릴아민 하이드로클로라이드(polyallylamine hydrochloride, PAH)와 인산 이온(phosphate ion)으로 구성된 나노 복합체는 최적화된 pH 조건에서 수소결합과 정전기적 인력 같은 강력한 상호작용을 통해 코어 입자에 코팅된다. 폴리아민 나노 복합체에 존재하는 PAH 주쇄의 아민 그룹들은 규산(silicic acid)의 축합(condensation) 반응을 촉매하여, 코어 입자 표면의 실리카 나노입자 성장을 시킬 수 있었다. 따라서, 본 방법을 통해 유기 코어에 무기 실리카 나노입자로 코팅된 유-무기 복합체 입자를 제조할 수 있었다. 최종적으로, 본 연구에서 제시한 방법은 보다 온화하며 환경친화적인 조건 하에서 단시간 내에 유-무기 복합체 입자를 합성할 수 있으며, 다양한 모양과 크기를 갖는 코어 입자에 적용되어 넓게 활용될 수 있다.

• 한국재료학회지
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• 제23권1호
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• pp.53-58
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• 2013

Superhydrophobic $SiO_2$ layers with a micro-nano hierarchical surface structure were prepared. $SiO_2$ layers deposited via an electrospray method combined with a sol-gel chemical route were rough on the microscale. Au particles were decorated on the surface of the microscale-rough $SiO_2$ layers by use of the photo-reduction process with different intensities ($0.11-1.9mW/cm^2$) and illumination times (60-240 sec) of ultraviolet light. With the aid of nanoscale Au nanoparticles, this consequently resulted in a micro-nano hierarchical surface structure. Subsequent fluorination treatment with a solution containing trichloro(1H,2H,2H,2H-perfluorooctyl)silane fluorinated the hierarchical $SiO_2$ layers. The change in surface roughness factor was in good agreement with that observed for the water contact angle, where the surface roughness factor developed as a measure needed to evaluate the degree of surface roughness. The resulting $SiO_2$ layers revealed excellent repellency toward various liquid droplets with different surface tensions ranging from 46 to 72.3 mN/m. Especially, the micro-nano hierarchical surface created at an illumination intensity of $0.11mW/cm^2$ and illumination time of 60 sec showed the largest water contact angle of $170^{\circ}$. Based on the Cassie-Baxter and Young-Dupre equations, the surface fraction and work of adhesion for the micronano hierarchical $SiO_2$ layers were evaluated. The work of adhesion was estimated to be less than $3{\times}10^{-3}N/m$ for all the liquid droplets. This exceptionally small work of adhesion is likely to be responsible for the strong repellency of the liquids to the micro-nano hierarchical $SiO_2$ layers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.393-393
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• 2012

Optically active nanostructures such as subwavelength moth-eye antireflective structures or surface enhanced Raman spectroscopy (SERS) active structures have been demonstrated to provide the effective suppression of unwanted reflections as in subwavelength structure (SWS) or effective enhancement of selective signals as in SERS. While various nanopatterning techniques such as photolithography, electron-beam lithography, wafer level nanoimprinting lithography, and interference lithography can be employed to fabricate these nanostructures, roll-to-roll (R2R) nanoimprinting is gaining interests due to its low cost, continuous, and scalable process. R2R nanoimprinting requires a master to produce a stamp that can be wrapped around a quartz roller for repeated nanoimprinting process. Among many possibilities, two different types of mask can be employed to fabricate optically active nanostructures. One is self-assembled Au nanoparticles on Si substrate by depositing Au film with sputtering followed by annealing process. The other is monolayer silica particles dissolved in ethanol spread on the wafer by spin-coating method. The process is optimized by considering the density of Au and silica nano particles, depth and shape of the patterns. The depth of the pattern can be controlled with dry etch process using reactive ion etching (RIE) with the mixture of SF6 and CHF3. The resultant nanostructures are characterized for their reflectance using UV-Vis-NIR spectrophotometer (Agilent technology, Cary 5000) and for surface morphology using scanning electron microscope (SEM, JEOL JSM-7100F). Once optimized, these optically active nanostructures can be used to replicate with roll-to-roll process or soft lithography for various applications including displays, solar cells, and biosensors.

• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.2051-2057
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• 2011

Several studies have demonstrated that nanoparticles (NPs) have toxic effects on cultured cell lines, yet there are no clear data describing the overall molecular changes induced by NPs currently in use for human applications. In this study, the in vitro cytotoxicity of three oxide NPs of around 100 nm size, namely, mesoporous silica (MCM-41), iron oxide ($Fe_2O_3$-NPs), and zinc oxide (ZnO-NPs), was evaluated in the human embryonic kidney cell line HEK293. Cell viability assays demonstrated that 100 ${\mu}g/mL$ MCM-41, 100 ${\mu}g/mL$ $Fe_2O_3$, and 12.5 ${\mu}g/mL$ ZnO exhibited 20% reductions in HEK293 cell viability in 24 hrs. DNA microarray analysis was performed on cells treated with these oxide NPs and further validated by real time PCR to understand cytotoxic changes occurring at the molecular level. Microarray analysis of NP-treated cells identified a number of up- and down-regulated genes that were found to be associated with inflammation, stress, and the cell death and defense response. At both the cellular and molecular levels, the toxicity was observed in the following order: ZnO-NPs > $Fe_2O_3$-NPs > MCM-41. In conclusion, our study provides important information regarding the toxicity of these three commonly used oxide NPs, which should be useful in future biomedical applications of these nanoparticles.

• 공업화학
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• 제28권1호
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• pp.1-7
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• 2017

폴리디메틸실록산(PDMS)은 화학적 증기 증착 방법을 통해 다양한 물질에 5 nm 두께 이하의 박막 형태로 증착될 수 있다. $SiO_2$, $TiO_2$, ZnO, C, Ni 및 NiO와 같은 다양한 종류의 나노입자 표면에도 PDMS 박막은 증기 증착을 통해 고르게 형성될 수 있으며, PDMS가 증착된 표면은 완벽한 소수성을 갖게 된다. 이 소수성 박막은 안정성이 높아 산, 염기 및 자외선 노출 시에도 잘 분해되지 않으며, 또한 PDMS로 코팅된 나노입자는 다양한 환경 분야에 응용될 수 있다. PDMS 코팅된 소수성 $SiO_2$ 입자는 기름/물 혼합액에서 기름과 선택적으로 반응하고, 기름 유출 사고 시 유류 확산을 억제할 수 있으며, 유출된 기름을 물에서 물리적으로 쉽게 분리할 수 있게 해준다. PDMS 코팅된 $TiO_2$를 진공 상태에서 열처리 할 경우 $TiO_2$ 표면은 완전하게 친수성으로 개질되며, 이때 $TiO_2$가 가시광선을 흡수하여 반응할 수 있게 하는 산소 빈자리 또한 발생하게 된다. PDMS 코팅 후 열처리한 $TiO_2$는 아무 처리하지 않은 $TiO_2$에 비해 가시광 하에서 수중의 유기 염료를 분해하는데 더 뛰어난 광촉매 활성을 보인다. 우리는 해당 연구에서 제시하는 간단한 PDMS 박막 코팅 방법이 다양한 환경 과학 및 공학 분야에서 응용될 수 있음을 소개하고자 한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.588-588
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• 2013

Nanoscale noble-metals have attracted enormous attention from researchers in various fields of study because of their unusual optical properties as well as novel chemical properties. They have possible uses in diverse applications such as devices, transistors, optoelectronics, information storages, and energy converters. It is well-known that nanoparticles of noble-metals such as silver and gold show strong absorption bands in the visible region due to their surface-plasmon oscillation modes of conductive electrons. Silver nanocubes stand out from various types of Silver nanostructures (e.g., spheres, rods, bars, belts, and wires) due to their superior performance in a range of applications involvinglocalized surface plasmon resonance, surface-enhanced Raman scattering, and biosensing. In addition, extensive efforts have been devoted to the investigation of Gold-based nanocomposites to achieve high catalytic performances and utilization efficiencies. Furthermore, as the catalytic reactivity of Silver nanostructures depends highly on their morphology, hollow Gold nanoparticles having void interiors may offer additional catalytic advantages due to their increased surface areas. Especially, hollow nanospheres possess structurally tunable features such as shell thickness, interior cavity size, and chemical composition, leading to relatively high surface areas, low densities, and reduced costs compared with their solid counterparts. Thus, hollow-structured noblemetal nanoparticles can be applied to nanometer-sized chemical reactors, efficient catalysts, energy-storage media, and small containers to encapsulate multi-functional active materials. Silver nanocubes dispersed in water have been transformed into Ag@Au nanoboxes, which show highly enhanced catalytic properties, by adding $HAuCl_4$. By using this concept, $SiO_2$-coated Ag@Au nanoboxes have been synthesized via galvanic replacement of $SiO_2$-coated Ag nanocubes. They have lower catalytic ability but more stability than Ag@Au nanoboxes do. Thus, they could be recycled. $SiO_2$-coated Ag@Au nanoboxes have been found to catalyze the degradation of 4-nitrophenol efficiently in the presence of $NaBH_4$. By changing the amount of the added noble metal salt to control the molar ratio Au to Ag, we could tune the catalytic properties of the nanostructures in the reduction of the dyes. The catalytic ability of $SiO_2$-coated Ag@Au nanoboxes has been found to be much more efficient than $SiO_2$-coated Ag nanocubes. Catalytic performances were affected noteworthily by the metals, sizes, and shapes of noble-metal nanostructures.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2425-2433
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• 2018

This study investigates a new organic based material and its dielectric and mechanical properties. It is a comprehensive nanocomposite comprising a combination of various types of nanofillers with hydrophobic silica nanoparticles (AEROSIL R 974) as a matrix modifier and a polyamide nano nonwoven textile, Ultramid-Polyamide 6, pulped in the electrostatic field as a dielectric barrier. The polymer matrix is an epoxy network based on diglycidyl ether of bisphenol A (DGEBA) and cycloaliphatic diamine (Laromine C260). The designed nanocomposite material is an alternative to the conventional three-component composites containing fiberglass and mica with properties that exceed current electroinsulating systems (volume resistivity on the order of $10^{16}{\Omega}{\cdot}m$, dissipation factor tan ${\delta}=4.7{\cdot}10^{-3}$, dielectric strength 39 kV/mm).

• 한국응용과학기술학회지
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• 제29권2호
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• pp.238-247
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• 2012

식품산업에서의 나노기술은 많은 연구와 가능성 있는 제품으로 새롭게 각광받는 분야이다. 나노와 마이크로 크기의 고체 입자는 유화된 오일 또는 물 입자를 함유하는 분산계의 처방에 적용 가능성이 매우 높은 것으로 인식되고 있다. 본 논문은 식용의 지방 결정, 실리카 나노 입자 및 생체 유래의 나노 결정체에 기반을 둔 식품 에멀젼의 성질과 개발에 관한 리뷰논문으로 다양한 피커링 안정화 분야에 관하여 검토하였다. 특히, 단백질로 안정화된 일반적인 에멀젼과 비교하여 Pickering 안정화 입자에 대해 초점을 맞추고자한다. 또한, 식품 산업에서 이들의 응용 예를 다루고자한다.

• 멤브레인
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• 제26권5호
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• pp.351-364
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• 2016

최근 폴리아마이드 선택층에 나노물질을 혼합하여 해수담수화 성능을 높이고자 하는 연구가 활발히 이루어지고 있다. 본 총설은 역삼투 분리막 해수담수화 공정에서의 에너지 효율 향상을 위한 우수한 성능을 가진 폴리아마이드 기반 나노복합막을 소개하고자 한다. 그래핀 옥사이드 및 탄소나노튜브와 같은 탄소나노물질 및 제올라이트, 실리카 나노입자 등의 다양한 나노물질들이 기존 폴리아마이드의 투과분리성능을 높이기 위해 적용되고 있다. 본 총설에서는 최근 연구 중인 각 나노소재별 성능향상 특장점을 소개하고, 더 높은 성능을 갖는 나노복합막 제조를 위한 연구방향을 제시하고자 한다.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.173-179
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• 2018

Electrochemical characterization was conducted on poly(vinyl alcohol) (PVA)-ceramic composite (PVA-CC) separators for supercapacitor applications. The PVA-CC separators were fabricated by mixing various ceramic particles including aluminum oxide ($Al_2O_3$), silicon dioxide ($SiO_2$), and titanium dioxide ($TiO_2$) into a PVA aqueous solution. These ceramic particles help to create amorphous regions in the crystalline structure of the polymer matrix to increase the ionic conductivity of PVA. Supercapacitors were assembled using PVA-CC separators with symmetric activated carbon electrodes and electrochemical characterization showed enhanced specific capacitance, rate capability, cycle life, and ionic conductivity. Supercapacitors using the $PVA-TiO_2$ composite separator showed particularly good electrochemical performance with a 14.4% specific capacitance increase over supercapacitors using the bare PVA separator after 1000 cycles. With regards to safety, PVA becomes plasticized when immersed in 6 M KOH aqueous solution, thus there was no appreciable loss in tear resistance when the ceramic particles were added to PVA. Thus, the enhanced electrochemical properties can be attained without reduction in safety making the addition of ceramic nanoparticles to PVA separators a cost-effective strategy for increasing the ionic conductivity of separator materials for supercapacitor applications.